A combustion chamber assembly unit, in which a bottom assembly unit is provided adjacent to an essentially cylindrical combustion chamber circumferential wall, is known from DE 10 2005 032 980 A1. This bottom assembly unit comprises as a central element a bottom part with a bottom wall and with a circumferential wall starting from the bottom wall in the radially outer edge area of said bottom wall. This bottom part thus has a generally pot-like structure, into which a porous evaporator medium is inserted. This means that the circumferential wall of the bottom area radially surrounds the porous evaporator medium, i.e., it extends, starting from the bottom wall, in the direction of the porous evaporator medium or along same. A wall part, which also extends radially over the combustion chamber circumferential wall on the outside and has a radially inwardly projecting flange area supporting axially the bottom part or its circumferential wall, also extends radially over the bottom part on the outside. The bottom part is held in axial contact with this flange area by a securing element provided on the rear side of the bottom part.